Monomer chromatin subunits (nucleosomes or nu 1 have been isolated and their responses to various conformational perturbants (i.e., ionic strength, pH, urea, ethanol, ethylene glycol, dioxane, DMSO, and other organic solvents) were examined by various biophysical and ultrastructural methods. Nu 1 has also been subfractionated in terms of salt-solubility, and microcrystals obtained, as a first step toward X-ray diffraction studies. Inner histones (H4, H3, H2A, H2B) have been isolated and examined as a function of salt and pH. Hydrodynamic studies document dimer-tetramer-octamer association states. Inner histones have been re-associated with various natural and synthetic DNAs, and the products characterized by biophysical techniques. Chromatin has been reacted with benzo(a)pyrene diol epoxide in vitro. Nuclease degradation studies localize the adduct as preferentially bound to the DNA between nu 1.